Alloys



Patented Feb} 6, 1940 UNITED STATES PATENT OFFICE Liebig, Arlington, N.

1., assignors to Baker &'

Company, Inc., Newark, N. J., acorporation of 7 New Jersey No Drawing.Application September-'13, 1939, Serial No. 294,646

7 Claims.

This application is a continuation in part of our application Serial No.231,754, filed September 26, 1938, allowed April 5, 1939, and thisinvention relates in general to alloys .and more particularly to alloysfor use in dentures and dental ically worked into suitable shapes, whichshall' have great hardness and high tensile strength to 15 take andretain a high polish and to withstand stresses, particularly such as areincident to use in dental appliances, and which shall have a hightemperature softening point so as topermit operations involving hightemperatures, such as sol- 20 daring, welding, casting other metalsagainst it, and the like, without the great strength being lost.

We have found that alloys of platinum, palladium, silver and gold areadmirably suited for 20 the purpose with the proportions of the metalsvarying from 20 to 60% platinum, from to 40% palladium, from 10 to 50%silver, and from 1 to 25% gold. If particularly great corrosionresistance is desired the combined content of platinum a0 and goldshould not fall below about 40% and as 40% palladium, from %to 50%silver and from 1% to gold, are desirable, while when great hardness andhigh corrosion resistance even toward contaminated acids are desired-theiollowing alloys are especially satisfactory:

40 (ll 40% platinum, 30% palladium, silver,

5% gold.

(2) 40% platinum, 25% palladium, 25% silver, 10% gold.

Those alloys having the gold content ranging- Experience has shown thatthese preferred alloys are resistant for extended periods or time toacids contaminated with iron and materials ausuallyoccurrinsinpicklingacidsusedindental laboratories, such asoxyphosphate cements, etc., even when in contact with other metals oralloys having a difierent electrical potential.

The alloys have been found to be highly resistant to corrosion andattack by acids including those acids most commonly used in dentistry,such as hydrochloric acid,.nitric acid and sulphuric acid, concentratedas well as dilute.

Also they have great hardnessand high tensile strength which isextremely desirable where denm) tal appliances are subject to stresses;for example the alloy containing 40% platinum,- palladium, 25% silver,5% gold has, when hard, an ultimate tensile strength of 168,000 poundsper square inch and a Rockwell hardness of 110 B 15 scale. Whilesumcient restoration of ductility for further working is obtained byheating below 1200 C., the alloys do not become dead soft until theyhave been heated above 1200 C. When heated at the lower temperaturessufiicient hard- 20 ness is retained to render the alloys particularlysuited for appliances subject to soldering and welding operations andfor appliances against which other metals or alloys are cast,especiallysince such operations are carried out at temperg5 atures of100 to 900 C. A clasp wire, for instance, may be soldered to dentures,or the dental metal or alloy may be cast against the clasp wire withoutdanger of softening of the metal of the wire and without danger ofoverheating which 30 might affect detrimentally the structure of thealloy.

It should be understood that the limited proportions above speciiied arenot critical and that suitable alloys may be formed with the metalproportions varying more or less from the maximum and minimum limitsspecifically stated.

Furthermore, the alloys may also contain small quantities, for exampleup to a few percent, of

any, other metal or metals which will not dele- I teriously aflect theiundamental characteristics of the alloys as described, such as anothermetal of the platinum group other than platinum and palladium, or; heavybase metals or metals contributing to age hardening such as tin, zincand 5 cadmimn.

The alloys are especially useful for dental devices that are used in themouth, such as orthodontia 'wirm, tooth bands, orthodontia locks,clasps, dentures and kindred devices.

Having thus described our invention, what we claim is:

- 1. An alloy of from twenty (20) to sixty (00) percent platinum, ten(10) to forty (40) peroentpalladlum, ten (10) toflity percent silu ver,and from one (1) to twenty-five (25) percent 801d.

2. An alloy of from twenty (20) to sixty (60) percent platinum, ten (10)to forty (40) percent palladium, ten (10) to fifty (50) percent silver,and from one (1) to twenty-five percent gold, wherein the combinedcontent of platinum and gold is not less than about forty (40) percentand the combined content of palladium and silver is not more than sixty(60) percent.

3. An alloy of about thirty to forty percent platinum, from abouttwenty-five (25) to thirty (30) percent palladium, about twenty (20) totwenty-five (25) percent silver, and from about ten (10) to twenty-five(25) percent gold.

4. An alloy composed of from twenty (20) to fifty percent platinum,fifteen (15) to forty (40) percent palladium, fifteen (15) to fifty (50)percent silver, and from one (1) to twenty (20) percent gold.

5. An alloy composed of from twenty (20) to fifty (50) percent platinum,fifteen (15) to forty (40) percent palladium, fifteen (15) to fifty (50)percent silver, and from one (1) to twenty (20) percent gold, whereinthe combined content of platinum and gold is not less than about forty(40) percent and the combined content of palladium and silver is notmore than about sixty percent.

6. An alloy composed of from twenty (20) to fifty (50) percent platinum,fifteen (15) to forty (40) percent palladium, fifteen (15) to thirtyfive(35) percent silver, and from one (1) to twenty (20) percent gold,wherein the combined content of platinum and gold is not less than aboutforty (40) percent and the combined content of palladium and silver isnot more than about sixty (60) percent.

7.An alloy consisting of about forty (40) percent platinum, irom abouttwenty-five (25) to thirty (30) percent palladium, about twenty-five(25) percent silver, and from about five (5) to ten (10) percent gold.

CECIL S. SIVIL. EDWARD O. LIEBIG.

